Fuel and air delivery adjusting means for oil burners



FUEL. AND AIR DELIVERY ADJUSTING MEANS FOR 011. BuRNERs Filed Oct. 22, 1951 'J. F. HlRTZ April 14, 1953 2 SHEETS-SHEET l IIIIIA FUEL PUMP PRESSURE CONTROL VA L VE April 14, 1953 J. F. HIRTZ v 2,634,805

FUEL 'AND AIR DELIVERY ADJUSTING MEANS FOR OIL BURNERS Filed Oct. 22, 1951 2 SHEETSSHEET 2 Patented Apr. 14, 1953 FUEL AND AIR DELIVERY ADJUSTING MEANS FOR OIL BURNERS John F. Hirtz, Watertown, Wis., assignor to Syncromatic Corporation, Watertown, Wis., a. corporation of Wisconsin Application October 22, 1951, Serial No. 252,447

4 Claims. (01. 158-76) This invention relates to oil burners of the type used in automatically controlled heating plants.

Generally speaking the amount of heat which is obtained from combustion of the fuel mixture projected into a combustion chamber by an oil burner depends upon the quantity of fuel discharged from its fuel nozzle per unit of time. In an oil fired heating plant installation, therefore, it is customary, by ascertainment of the volume of the space to be heated, to adjust the burner for consumption of that quantity of fuel per unit of time which will satisfy all the demands likely to be made upon the heating plant. Hence, it is not only necessary to provide some means for adjusting the quantity of fuel discharged from the fuel nozzle of the burner, but provision must also be made for adjusting the volume of air discharged from the air nozzle of the burner for admixture with the fuel.

The purpose of these adjustments, obviously, is to enable the attainment of an air-fuel ratio which will give the most heat from the fuel discharged by the burner.

In many oil burners the volume of air discharged from the air nozzle to support combustion is adjustable by means of a damper located at the zone of communication between the lower housing and the air nozzle. Opening of this damper, of course, enables a greater volume of air to travel through the air nozzle of the burner, While adjustment of the damper toward a closed position decreases the volume of air flowing through the air nozzle.

Heretofore, adjustment of the burner for consumption of different quantities of fuel involved replacement of the fuel nozzle with one having either a larger or smaller discharge orifice, as the situation demanded; or the adjustment sought was effected by a slug having a metering orifice of the required size, placed in the outlet of the fuel pump or in the fuel line leading to the fuel nozzle. It was impractical to effect adjustment of the fuel quantity by adjustment of the pressure thereon since any reduction in the fuel pressure below a predetermined minimum entailed the risk of having the orifices clog and would seriously affect the pattern of the fuel sprayed from the fuel nozzle. In either case, therefore, the fuel was fed into the fuel nozzle at a constant high pressure.

Recently, however, a way has been found by which adjustment of the quantity of fuel discharged from the fuel nozzle per unit of time could be accomplished through regulation of the fuel pressure, without danger of clogging the discharge orifices of the fuel nozzle or affecting the spray pattern.

This pressure regulated type of fuel discharge has the advantage of eliminating the need for adjustment of the fuel nozzle by such expedients as exchanging one fuel nozzle for another or substitution of slugs having different size metering orifices and located in the pump outlet or the pressure line leading to the fuel nozzle.

With this pressure regulating scheme, a bypass line is provided for returning fuel to the supply from a point directly adjacent to the discharge orifice of the fuel nozzle, and the quantity of fuel discharged from the fuel nozzle is regulated by adjusting the setting of a metering valve in the bypass line. Depending upon the extent to which the metering valve is open, therefore, a quantity of the fuel introduced into the fuel nozzle will be led out of the nozzle and bypassed to the fuel tank, while the remainder of the fuel Will be discharged from the nozzle under a pressure determined by the setting of the adjustable metering valve.

Despite the fact that very accurate adjustments of the fuel quantity discharged by the burner were possible with the pressure modulated fuel nozzle described, it was impossible prior to this invention to achieve efiicient combustion of the fuel at all settings of the metering valve. Though it would appear that adjustment of the air damper to provide the most advantageous air-fuel ratio for efficient combustion should have solved this problem, actually it had very little beneficial effect upon the combustion characteristics of the burner.

It is the main object of this invention, therefore, to provide an oil burner, equipped with a pressure modulated fuel nozzle of the type described, wherein the burner is constructed to assure the achievement of highly efiicient combustion of the fuel throughout the entire range of fuel discharge adjustment. 7

More particularly it is an object of this invention to provide an oil burner of the character described in which means is provided for adjusting the velocity as well as the volume of air discharged from the air nozzle of the burner for mixture with whatever quantity of fuel is discharged from the pressure modulated fuel nozzle of the burner but without altering the flame pattern or its characteristics so as to assure efficient combustion of the fuel.

With the above and other objects in view, which will appear as the description proceeds,

this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a longitudinal sectional view through an oil burner constructed in accordance with the principles of this invention;

Figure 2 is a cross sectional view taken through the discharge end of the burner along the plane of the line 22;

Figure 3 is a fragmentary elevational View of a portion of the air nozzle of the burner;

Figure 4 is a longitudinal sectional view through the pressure regulated fuel nozzle and diagrammatically illustrating the manner in which the quantity of fuel discharged therefrom may be regulated;

Figure 4a is a perspective view of the front end portion of the fuel distributor of the fuel nozzle;

Figure 5 is a group perspective view of the elements of the burner which cooperate to determine the velocity of the air discharging from the air nozzle of the burner;

Figure 6 is a longitudinal sectional view on the order of Figure 1 but illustrating the adjustment of the burner for producing a large flame for maximum heating; and

Figure 6a is a view similar to Figure 6 but showing the adiustment of the burner for producing a small flame for minimum heating.

Referring now more particularly to the accompanying drawings in which like numerals identify like parts throughout the several views, the numeral 5 generally designates the hollow cylindrical air nozzle of an oil burner having its inlet end connected with the housing 5 of a blower I. The blower forces air through the air nozzle in a volume depending upon the adjustment of a damper 8 at the junction of the blower housing and the air nozzle. The damper 8 may be adjusted as by rreans of a screw 9, accessible from the exterior of the oil burner.

The air forcefully fed into the air nozzle by the blower issues from a port I I in the discharge end of the air nozzle for admixture with the fuel discharging from the fuel nozzle I2.

The fuel nozzle I2 is supplied with fuel from a fuel tank or other source I4 through a supply duct I5 connected between the pressure outlet of a pump I6 and the fuel nozzle. The fuel nozzle is mounted in the discharge end of the air nozzle, coaxially thereof, by means of a support I8 through which the supply duct I5 passes. The support I8 rests upon the wall of the air nozzle and forms part of an axially ad ustable diffusing head I9 located in the forward or discharge end port on of the air nozzle.

Since the fuel supply duct I5 is rigidly attached to the fuel nozzle I2 and locked to the support I8 in anv suitable manner, as by a set screw 20, it follows that the fuel nozzle is held coaxially of the air nozzle and in an axial position therein determined by'the adjustment of the diffusing head I 9.

Referring to Figrre 4 it will be seen that the fuel nozzle I2 is pro ided with suitablv screened passages by which the fuel is led. into a small Ill funnel shaped chamber I2 in the outer end portion of the fuel nozzle from which it discharges through a small axial orifice 2| in the extremity of the nozzle. The chamber I2 is defined by the front end of a distributor 22 and the conical inner surface of the fuel nozzle against which the distributor seats. As best shown in Figure 4a the distributor has a plurality of slits 22' in its conical front surface to communicate the screened fuel passages with the chamber I2. The disposition of these slits governs the spray pattern of the fuel leaving the nozzle, and to assure the maintenance of the desired pattern the pressure under which the fuel enters these slits is held constant.

An axial passage 23 leads from the chamber I2 back through the distributor to a branch passage 23' leading out through the side of the nozzle to conduct some of the fuel brought into the chamber I 2' under pressure into a bypass duct 24 for return to the fuel tank I4 through an adjustable metering valve 25 in the duct 24. The type of nozzle described is known as a pressure modulated nozzle wherein the quantity of fuel to be discharged through the orifice 2I can be regulated by adjustment of the metering valve 25. This is easily done by a workman installing the oil burner since the metering valve can be placed in a readily accessible location and adjusted by means of a screw driver inserted in a slot in an adjusting screw 26 on the valve.

The bypass duct 24 like the fuel supply duct I5 extends rearwardly from the fuel nozzle I2 to pass through a suitable aperture in the support I8, and both the supply and bypass ducts pass outwardly through a longitudinally elonsated slot 28 in the side wall of the air nozzle 5 adjacent to the blower housing 6. As shown best in Figures 1 and 3 the ducts I5 and 24 are secured to an adjusting plate 30 overlying the slot 28 at the exterior of the air nozzle. This plate may be held in different positions of ad justment longitudinally of the air nozzle by a locking screw 3I threaded into the side wall of the air nozzle and passing through an elongated slot 32 in the plate substantially parallel to the slot 28.

With this construction shifting of the plate 30 forwardly or rearwardly of the air nozzle 5 carries the diffusing head I9 and the fuel nozzle I2 forwardly toward or rearwardly from the discharge port I I in the air nozzle.

The diffusing head includes a cylindrical wall or shell 34 which surrounds the fuel nozzle. The connection between the cylindrical wall or shell 34 and the fuel nozzle support I8 positions the shell in coaxial radially spaced relationship with the fuel nozzle as well as with the air nozzle. The forward end portion of the shell 34, however, is slidably received in and guided by a series of spirally disposed vanes 36 formed on the inside of a flange 31 fixed to the discharge end of the air nozzle 5 directly inwardly of its port II.

The radially innermost edges of these vanes 36 throughout their length terminate on a circle of a diameter substantially corresponding to that of the exterior of the shell 34 and project rearwardly a distance from the port II such as to have their rear edges disposed farther rearwardly in the air nozzle than the front end of the shell 34 in the rearmost position of adjustment of the diffusing head seen in Figure 6. Accordingly, regardless of the position of the shell 34, it always coacts with the vanes 36 to form separated spiral air passages which impart a spiral twisting or whirling motion to the discharging air which breaks up the fuel particles with the same effectiveness throughout the range of adjustment of the fuel discharge. This, plus the fact that the fuel nozzle [2 moves with the shell 34 assures the maintenance of the desired flame pattern and flame characteristics.

The flange 3? is secured to the discharge end of the air nozzle in any suitable manner and has a cylindrical wall portion 38 in telescoping relation with the front end of the air nozzle. A relatively flat front wall 39 on the flange 3'1 normal to the axis of the air and fuel nozzles, connects with the cylindrical wall portion 38 by means of a generously curved wall portion 50. The port I! which defines the discharge opening in the outer end of the air nozzle is formed in this flat front Wall 39 of the flange and it is essential to the success of this invention that the diameter of the port ll be substantially the same as that of the exterior of the shell 34.

The shell 34 of the diffusing head cooperates with the wall of the air nozzle to define an annular air passage 42 surrounding the difiusing head which is connected through the spiral passages between the vanes 35 with the space which is always maintained between the front end of the diffusing head and the front wall 39 of the flange 35. This space ahead of the diffusing head provides a radial air passage 43 through which the spirally moving air leaving the passages between the vanes 36 must pass for discharge from the port ll of the air nozzle. As the air enters the radial air passage 43, however, its direction of travel is changed abruptly by the curved wall portion 40 on the flange and the front wall portions 39 surrounding the discharge port I I so that the air is caused to travel substantially sharply radially inwardly toward the fuel nozzle l2.

Some of the air flowing through the annular air passage 42 is acted upon by scoops 45 struck from the side wall of shell 34 and is deflected thereby into the interior of the diffusing head to pass over the exterior surfaces of the fuel nozzle in intimate contact therewith.

For an intermediate setting of the fuel metering valve 25 the air damper 8 and the diffusing head must be in the positions of adjustment shown in Figure 1. With this setting of the parts not only is volume of the air correctly proportioned with the quantity of fuel discharged from the fuel nozzle but in addition the velocity and direction of the air leaving the port H as determined by the axial dimension of the radial air passage 43 is correct for the achievement of the most efficient combustion.

If it is desired to increase the size of the flame for greater heat output the metering valve 25 is adjusted to further restrict the bypass line 24 and increase the pressure in the chamber I2 to correspondingly increase the quantity of fuel discharged through the orifice 2l. This, of course, also increases the rate at which the fuel issues from the fuel nozzle. With the fuel nozzle set to discharge a greater ouantity of fuel per unit of time, the volume of air su plied to support combustion must be correspondingly increased which is done by opening the dam er 8 the required amount; but to maintain the optimum flame characteristics and combustion efficiency the effectiveness of the spiral vanes 36 must not be diminished and the velocity of the discharging air must be kept at a redetermined rate. This is accomplished by adjustment of the diffusing head together with the fuel nozzle 12 rearwardly in the air nozzle away from the discharge end thereof to increase the axial dimension of the radial air passage 43 as shown in Figure 6. This allows a greater volume of air to flow out the discharge port H of the air nozzle without increasing its velocity and without loss of effectiveness of the spiral vanes 36.

Conversely, if it is desired to reduce the quantity of fuel discharged per unit of time the metering valve 25 is opened to. allow more fuel to be bypassed to the supply 14; and the damper 8 is adjusted as shown in Figure 6a to correspondingly reduce the volume of air supplied. However, the velocity of the discharging air must not be changed. Hence, the size of the radial air passage 43 must be reduced by shortening the axial length thereof to offset the reduction in volume of air supplied. This is accomplished by sliding the diffusing head and fuel nozzle to its forward position shown in Figure 6411.

Tests have demonstrated that the burner of this invention not only makes possible for the first time successful use of a pressure modulated fuel nozzle, but in addition actually achieves a marked increase in efficiency over the conventional high pressure injection type oil burner. The results of one of these comparative tests are given below. This test compared a highly efficient conventional oil burner with the oil burner of this invention, the two being successively installed in the same furnace with instrument locations unchanged. In each instance #2 fuel oil having a caloric value of 135,400 B. t. u. per gallon was consumed at the rate of .99 gallon per hour to provide a B. t. u. input of 134,000, with a stack draft of .03 in. H2O. The following comparative results were obtained:

Direct Efficiency d l While other factors may have some bearing upon the success of this invention, it has been discovered that there must be not only a proper proportioning of fuel and air to achieve the best ratio for combustion, but that the velocity of the discharging air must also be kept constant throughout the entire range of fuel discharge rates; and to achieve this control over the air velocity the diameters of the air discharge port H and the axially adjustable shell must be substantially the same and in all positions of adjustment of the shell it must maintain its sliding engagement with the inner edges of the vanes 36 to thereby separate the spiral passages between the vanes from one another.

In addition, the flame characteristics and pattern must be substantially the same for all rates of fuel consumption, and this is assured in the present invention by providing not only for the control of air volume and velocity, but also for control of such factors as the direction of air discharge from the burner and the axial position of the fuel nozzle with respect to the air discharge port.

From the foregoing description taken together with the accompanying drawings, it will be readily apparent to those skilled in the art that the oil burner of this invention, by providing means for correctly relating the three factors, (1) quantity of fuel discharged per unit of time, (2) volume of air and (3) velocity of the air at the point of discharge, makes possible the successful use of the so-called pressure modulated type fuel nozzle and achieves a marked improvement in efliciency over the conventional high pressure injection type oil burner.

What I claim as my invention is:

1. In an oil burner: an air nozzle; a blower connected with the air nozzle remote from its discharge end; means for adjusting the volume of air forced through the air nozzle by the blower; means defining an abrupt constriction at the discharge end of the air nozzle providing an air discharge port of fixed diameter; a plurality of spiral vanes fixed within the discharge end portion of the air nozzle and extending a substantial distance back from its discharge port, the front ends of said vanes being contiguous to the edge of the air discharge port and the inner edges of the vanes throughout the length thereof lying upon a cylinder of a diameter substantially that of the air discharge port; a cylindrical shell within the discharge end portion of the air nozzle, said shell having its front end open and having restricted air inlet means rearwardly of its open front end and the diameter of said shell being substantially the same as that of the air discharge port; means mounting the shell coaxially to the air discharge port and for axial adjustment thereof within the air nozzle so that the communication between the air discharge port and the spaces between the spiral vanes provided by the space between the front end of the shell and the edge of the air discharge port may be increased or decreased, the shell having sliding engagement with the inner edges of the spiral vanes throughout its range of adjustment; a fuel nozzle disposed coaxially within the shell and fixed with respect thereto; means connected with the fuel nozzle for feeding fuel under pressure thereto; a manually adjustable bypass leading from the fuel nozzle whereby the quantity of fuel discharged from the fuel nozzle per unit of time may be correlated with the volume of air forced through the air nozzle; and means for adjusting the shell and with it the fuel nozzle axially of the air nozzle to thereby adjust the size of the air passage provided by the space between the front end of the shell and the air discharge port and thus correlate the velocity of the discharging air with the selected fuel and air adjustment without loss of effectiveness of the spiral vanes.

2. In an oil burner having a blower fed air noz-' zle and means for manually adjusting the volume of air fed by the blower to the nozzle, the combination of means defining an abrupt constriction at the discharge end of the air nozzle providing an air discharge port of fixed diameter; a plurality of spiral vanes fixed within the discharge end portion of the air nozzle and extending back from its discharge port, the front ends of said vanes being contiguous to the edge of the air discharge port and the inner longitudinal edges of the vanes throughout their length lying upon a cylinder of a diameter substantially that of the air discharge port; a cylindrical shell of substantially the same diameter as the air discharge port axially adjustable within the discharge end portion of the air nozzle with its outer surface in sliding engagement with the inner longitudinal edges of the spiral vanes, said shell having its front end open and having restricted air inlet means rearwardly of its open front end and being sufficiently longer than the spiral vanes to assure maintenance of its sliding engagement with the vanes throughout its range of spiral adjustment; a fuel nozzle having an orifice of a size appropriate for a predetermined maximum rate of fuel discharge; means for feeding fuel to the orifice at a predetermined pressure which is suflicient to maintain the maximum rate of fuel discharge through said orifice; manually adjustable pressure releasing means leading from a point directly adjacent to the inlet side of the orifice for regulating the pressure under which fuel is discharged from the orifice to thereby adjust the quantity of fuel discharged by the fuel nozzle per unit of time, so that fuel and air discharge may be correlated to effect a desired rate of fuel consumption within the capacity of the burner; and means for adjusting the shell axially toward and from the air discharge port to thereby adjust the velocity of the air flowing from the separate spiral passages between the vanes and through the air discharge port, whereby the velocity of the discharging air may be correlated with the selected fuel and air adjustment without loss of effectiveness of the spiral vanes.

3. In an oil burner having a blower fed air nozzle, means for adjusting the volume of air delivered by the blower to the air nozzle, a pressure fed fuel nozzle within the air nozzle and arranged to discharge fuel into the air issuing from the air nozzle and means for adjusting the quantity of fuel discharged from the fuel nozzle per unit of time, so that the fuel and air discharge may be correlated to effect a desired rate of fuel consumption, means for controlling the air as it issues from the air nozzle comprising: means defining an abrupt constriction at the discharge end of the air nozzle providing an air discharge port of fixed diameter; a plurality of spiral vanes fixed within the discharge end portion of the air nozzle and extending back from its discharge port, the front ends of said vanes being contigu ous to the edge of the air discharge port and the inner longitudinal edges of the vanes throughout their length lying upon a cylinder of a diameter substantially that of the air discharge port; a cylindrical shell of substantially the same diameter as the air discharge port surrounding the fuel nozzle and axially adjustable within the discharge end portion of the air nozzle with its outer surface in sliding engagement with the inner longitudinal edges of the spiral vanes, said shell having its front end open and having restricted air inlet means rearwardly of its open front end and being sufiiciently longer than the spiral vanes to assure maintenance of its sliding engagement with the vanes throughout its range of axial adjustment; and means for adjusting the shell axially toward and from the air discharge port to thereby adjust the velocity of the air flowing from the separate spiral passages between the vanes and through the air discharge port, whereby the velocity of the discharging air may be correlated with the selected fuel and air adjustment without loss of effectiveness of the spiral vanes.

4. In an oil burner having an air nozzle and a fuel nozzle therein, means for controlling the air as it discharges from the nozzle comprising: means defining an abrupt constriction at the discharge end of the air nozzle providing an air discharge port of fixed diameter; a plurality of spiral vanes fixed within the discharge end portion of the air nozzle and extending back from 9 its discharge port, the front ends of said vanes being contiguous to the edge of the air discharge port and the inner longitudinal edges of the vanes throughout their length lying upon a cylinder of a diameter substantially that of the air discharge port; and a cylindrical shell of substantially the same diameter as the air discharge port adapted to surround the fuel nozzle and axially adjustable within the discharge end portion of the air nozzle with its outer surface in sliding engagement with the inner longitudinal edges of the spiral vanes, said shell having its front end open and having restricted air inlet means rearwardly of its open front end and being sulficiently longer than the spiral vanes to assure maintenance of its sliding engagement with the be regulated Without loss of efiectiveness of the spiral vanes.

JOHN F. HIRTZ.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,163,915 Reif et al June 27, 1939 2,298,745 Klockau Oct. 13, 1942 2,393,897 Glendenning Jan. 29, 1946 2,575,613 Boarman Nov. 20, 1951 2,585,081 Bernhard Feb. 12, 1952 2,590,111 MacCracken et a1. Mar. 25, 1952 

